The present invention relates to an electric motor drive control method and apparatus.
An electric motor serves to drive a vehicle (traction) and apply a braking force to the vehicle (regeneration). Development of the vector control technique has allowed various types of electric motor control to be smoothly performed with precision. Recently, a three-phase AC motor such as a three-phase induction motor, a permanent magnet synchronous motor and the like has been employed to control the motor under a vector control. Japanese Patent Application Publication No. JP-A-2005-192341 discloses a permanent magnet synchronous motor structured to be mounted on a hybrid vehicle. Japanese Patent Application Publication No. JP-A-2006-14539 discloses a mode of the vector control with respect to the electric motor of the aforementioned type.
The permanent magnet synchronous motor is provided with a rotor equipped with a permanent magnet and a stator equipped with stator coils at a U-phase, V-phase and W-phase. In Japanese Patent Application Publication No. JP-A-2006-14539, the electric motor is connected to a drive control unit for the purpose of generating a drive motor torque serving as a torque of the drive motor or a generator torque serving as a torque of the generator. The control unit transmits pulse width modulation signals (PWM pulse) at the U-phase, V-phase and W-phase to an inverter. The inverter supplies the phase current, that is, the electric current at the U-phase, V-phase and W-phase to the respective stator coils so as to generate the drive motor torque and the generator torque.